1. Field of the Invention
The present invention relates generally to orthodontic devices, and more particularly to a mandibular arch developer for moving the lower teeth of an individual in better alignment with the upper teeth.
2. Description of the Prior Art
Mandibular arch developers are used by orthodontists to move the lower teeth of an individual in better alignment with the upper teeth. This is done by lengthening and widening the jaw through application of force in specific locations on an individual's lower teeth and bone with an orthodontic appliance. The appliance can be either fixed or removable. Most of the individuals or patients using this apparatus are children, and the growth of the patient contributes to the movement of the mandibular arch. However, in some situations it is desired to move the teeth in the lower jaw of an adult. Regardless of the patient's age, these devices are used to move the lower teeth into alignment with the upper teeth and/or jaw.
In some cases, a device is necessary for expanding the position of the teeth in the lower jaw of an individual, so that the lower teeth will line up with the upper teeth prior to the placement of braces. Some of these devices may be also used to lengthen the lower jaw and allow adequate space for alignment of the lower teeth. The speed and amount of tooth movement of these devices can be effected by the growth of an individual. Other devices are adjustable by an orthodontist prior to installation in the mouth. Most of these devices require multiple mechanical parts that must be precisely machined. Many of these devices are not adjustable once they are cemented in the mouth, or may only be adjustable in a single direction. Devices that are used to both widen and lengthen the arrangement of teeth in the jaw can cause unwanted rotation of the molar teeth during the expansion process. Further, the molar teeth of some individuals are already rotated to undesired positions. None of the prior art mandibular arch developers address the problem with the unwanted rotation and/or the unwanted rotated position of the molar teeth.
It is known in the prior art to use a device known as a lip bumper. The lip bumper is used to widen and lengthen the arrangement of teeth in the jaw, but depends solely on the growth and muscle function of the patient to work. The lip bumper is placed between the lower teeth and the lower lip of a patient. As the patient grows, the jaw will move forward and force the bumper to make contact with the lip causing the arch to widen and lengthen. The lip bumper is completely dependent on the growth rate of the child and cannot be used on adults. The dependency on the growth rate of the child can cause unpredictable and inconsistent results. Further, the lip bumper has been known to occasionally cause sores in the patient's mouth resulting in pain and discomfort.
Other devices are known that are adjustable by an orthodontist and are not completely dependent on the growth rate of a patient. For example, U.S. Pat. No. 4,573,914 discloses a fixed type formative orthodontic appliance employed to increase dental arch size and overcome crowded teeth. The patent teaches both a lower and an upper appliance. The lower appliance includes an arch wire that applies force to the lower incisors by means of an arm assembly connected to oppositely disposed molar bands. A special screw assembly is located on the arm assembly adjacent each molar band. Fixedly adjoined to each of the bands is a clasp that extends along the pre-molars and applies an outward force to the teeth from the molar to the pre-molar area. The arch of the clasp is set prior to installation of the device into a patient's mouth and is not adjustable once installed. The special screw assembly attached to the arm is adjustable to vary the force on the incisors for lengthening the jaw. The device is a permanent fixture and allows access to the screw assembly, such that adjustment may be made while the appliance is in place in the patient's mouth in the lengthening direction. The screw and arm assembly is made of precisely machined parts. The device may cause the molar teeth to rotate as the device expands the mandibular arch.
U.S. Pat. No. 5,645,422 discloses a lower mandibular arch expander having a mid-arch expansion screw positioned between two forward orthodontic bands adapted to be attached to the mandibular first primary molars. A spring loaded rod and tube assembly extends between each of the front bands to a rear orthodontic band attached to the permanent first molar. The spring loaded rod and tube assembly includes a hollow tube extending from the rear orthodontic band adapted to receive a rod extending from the front orthodontic band. A coil spring is positioned around the rod and the rod is slidingly engaged in the tube. The coil springs have a preset tension that is selected by the orthodontist to affect the appropriate distal arch length development in the bicuspid area. Once this spring is set and the device installed in the mouth of the patient, the spring is no longer adjustable. The expansion screw is the only adjustment means associated with this device once the device is installed in the patient's mouth. The device will cause the rotation of the molars during mid-arch expansion. Further, the device requires two front orthodontic bands that can be seen in the patient's mouth by an observer.
The current invention eliminates the problems with the prior art by providing a mandibular arch expander that applies not only linear forces in the widening and lengthening directions, but also a rotational force about an axis of the molar tooth. The forces are applied at lower positions on the teeth than prior art devices. This application of force at a lower position eliminates tipping of the molar and provides for better centering. The device lengthens and widens the position of teeth in the lower jaw, while also rotating the molars back to their original position or to an improved position during the expansion process. The device is inexpensive and simple to make, is permanently affixed inside the patient's mouth once installed, can be used on children and adults, does not cause sores in a patient's mouth, is not noticeable by the ordinary observer while in a patient's mouth and is simple to adjust in all three directions in or out of the patient's mouth.